Speed, Forces, Friction and Pressure (Worksheet 2) Answers
Forces
Forces can be applied to objects and can cause the object to: Start or stop moving, Speed up or slow down,
or Change direction. Most forces are applied through physical
contact. However you need to be aware of two forces that can be applied to an
object without any physical contact being applied.
These two forces are gravity and magnetism.
Measuring Forces
| Force can be measured using a Newton
meter. The Newton meter consists of a spring and a scale; the scale measures
how much the spring stretches when a force is applied to it.
The larger the force the more the spring extends. Force is measured in Newtons. An average sized apple has a weight of approximately 1N (Newton). |
|
Forces and Acceleration
The size of acceleration is dependent on the size of the force and the size of
the mass of the object. The four main rules to remember are:
A small force will give a small acceleration.
A LARGE force will give a large acceleration.
A small mass will lead to a large acceleration.
A LARGE mass will lead to a small acceleration.
Balanced and Unbalanced Forces
If several forces are applied to the same object, they may cancel each other
out. In this case the forces are balanced. When balanced forces are applied to
an object they will have no effect on its motion. If the object in this case is
stationary, it will remain stationary. If balanced forces are applied to a
moving object, the object will continue moving at the same speed and in the same
direction.
Examples of balanced forces include simple things such as a book resting on a
table. The weight of the book (gravity - downward force) equals the reaction
from the table (upward force) leading to the object being stationary.
If the forces applied to an object do not cancel each other out, they are
unbalanced and hence will have an effect on the motion of the object.
Friction and Air Resistance
Whenever an object tries to move, friction is present. Friction is present when
two surfaces are gripping. This is called static friction. When two surfaces are
sliding over each other the friction present is called sliding friction.
Friction acts in the direction that opposes motion. Therefore if a car is moving
forward the friction occurs in the reverse direction between the tyres and the
road surface.
Friction can be reduced through streamlining and lubrication. Streamlining is
where the shape of the object is such that it cuts through the air with less
resistance. Lubrication is where a substance is applied between the two surfaces
to reduce friction.
Continuous friction between surfaces can lead to them wearing away. In addition
friction can cause an increase in temperature (heat).
Answers:
| 1. | GRAVITY AND MAGNETISM |
| 2. | NEWTON METER |
| 3. | IN NEWTONS |
| 4. | IT WON'T CHANGE DIRECTION
SINCE FORCES ARE BALANCED |
| 5. | START OR STOP MOVING, SLOW
DOWN, SPEED UP, CHANGE DIRECTION |
| 6. | YES |
| 7. | LARGE ACCELERATION |
| 8. | SMALL ACCELERATION |
| 9. | STREAMLINING AND LUBRICATION |
| 10. | WEAR AND HEAT |
